U.S. Pat. No. 4,962,766 discloses a nerve locator and evaluator which is used in surgical procedures. An AC energizing current is transmitted through an electrical lead to the patient. High and low settings are available and the device is equipped with an auditory signal to alert the surgeon when current is flowing through the patient's body.
However, despite the progress provided by the device disclosed in U.S. Pat. No. 4,962,766, the device has been found to be unsatisfactory for a number of reasons. First, the device is mono-polar and is equipped with a single electrode at the evaluation tip. As a result, the device requires a secondary ground wire that exits the back end of the handpiece. The ground wire attaches the patient's body with a conductive patch or needle electrode. This arrangement is problematic because the needle can fall out or the patch can peel off during the procedure. Further, the ground wire can extend across the surgical area and become entangled with other instruments during the surgical procedure. Consequently, the ground wire can become dislodged and the device temporarily inoperable during surgery. As a result, there is a need for an improved nerve locator and evaluator which does not require the employment of a ground wire or lead.
Still further, the tip of the device disclosed in U.S. Pat. No. 4,962,766 is applied directly to the patient. Because it is employed during a surgical procedure, excessive amounts of blood and fluid are typically present. The blood and fluid makes it difficult for the surgeon to see the exact area where the distal tip of the device is being applied. Consequently, it can be difficult for the surgeon to make visual contact with the nerve that is being located or stimulated because of the presence of the blood and fluid. In addition to enhancing the surgeon's visualization of the nerve under investigation, removal of blood and fluid would also be important to electrically isolate the nerve prior to location or evaluation and further to prevent any electrical shunting of current applied to the nerve. As a result, there is a need for an improved nerve locator and evaluator which has a built-in mechanism for removing excess blood and fluid from an area under observation or investigation.
Similarly, the device disclosed in U.S. Pat. No. 4,962,766 is not equipped with any sort of a light source to assist the surgeon in viewing the distal end of the instrument tip. As a result, there is a need for an improved nerve locator and evaluator that is equipped with a built-in illumination means.
Finally, while the device disclosed in U.S. Pat. No. 4,962,766 has high and low current settings, the device does not incorporate preset evaluation parameters which allow for locating and evaluation. As a result, there is a need for an improved nerve locator and evaluator with predetermined settings for frequency, evaluation pulse duration and amplitude for the separate operations of nerve evaluation and nerve location.